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Fatigue Damage Spectrum

Predict a product’s life expectancy through accelerated testing

Use recorded data to create an accelerated random test that represents a lifetime of fatigue damage. The user sets the configurable parameters, and the FDS software handles the rest. With one click, you can control a new test profile on a shaker system.

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Part number 9209

VR9209

Accurate Test Acceleration

Vibration Research’s innovative FDS software reduces test time from analysis to control. Set the target life based on product specifications and the test duration and define the slope of the s/n curve and quality factor (Q). The software automatically calculates the correct ratios to produce the same fatigue damage in a user-defined test duration.

  • Calculation through the time-domain (not frequency) to account for real-world kurtosis
  • Displays peak acceleration, velocity, displacement, and kurtosis to quickly determine waveform statistics
  • Includes Random Import (VR9204) to compare methods of random profile generation

Importing time-waveforms with fatigue damage spectrum software

With one mouse click, control the newly created test profile on a shaker system within VibrationVIEW. Move from a time waveform to a breakpoint profile and control the profile all in one program.

Patented Kurtosis Control

The greatest damage potential is typically at peak acceleration levels. When the kurtosis value of a vibration signal is increased, the time spent at peak levels also increases. With kurtosis control, your test will better reflect what occurs in the real world.

Vibration Research’s patented kurtosis control, Kurtosion®, spreads damage over the fatigue damage spectrum rather than adding it to high frequencies only. Increasing just the kurtosis parameter will increase the damage experienced at higher frequencies, but a transition frequency parameter allows an adjustment to where the damage is placed.

Combine Multiple Waveforms

Create a random PSD profile that includes multiple input time-history files. Files can be weighted individually by time or cycles to create a total target life for the product. Combine methods include sum, envelope, or per-file envelope.

The software uses the same m, Q, and frequency range when combining data to create an equal relationship between each imported file. The output PSD will be the damage equivalent of the imported files and is generated from the target life for each waveform and the FDS settings.

  • Display profile statistics
  • Enable Kurtosion®
  • Export data to a .csv or .txt file, including damage vs. frequency and file statistics for each FDS
  • Create a breakpoint table
  • Copy & paste the FDS list to a spreadsheet program such as Microsoft Excel®

VR Papers and Presentations (PDF)

When Should I Use FDS?

With the FDS software, engineers can create a random test profile that is the damage equivalent to weighted time-history files from the product’s end-use environment. They can also compare multiple test failures, compare specifications to real-world data, and determine if current testing is valid (or over/under-testing).

If you’re asking these questions, you need FDS

  • What is the best random test to simulate my product’s environment?
  • How long should I be running my random test?
  • Can I accelerate my testing?

What is the Fatigue Damage Spectrum?

The fatigue damage spectrum is a random vibration spectrum based on Miner’s rule of damage. Miner’s rule states that fatigue damage will accumulate over time until it reaches a level that causes a crack or other deformation of a product.

The Fatigue Damage Spectrum software is a test development tool that replicates the operational environment of a product. It is used to create an accelerated random test using real-world data. The resulting test is the damage equivalent to a product’s lifespan.

For test purposes, the FDS can then be converted into a power spectral density (PSD) using Henderson-Piersol’s potential damage spectrum. The result is a single PSD profile for multiple time-history files. The FDS-generated PSD is a cumulative spectrum that represents the relative damage experienced by the product for all the combined and weighted environments.

FDS Video Demonstrations

Video 1 of 3

GM Case Study - FDS - Part 1 thumbnail

GM Case Study - FDS - Part 1

Analyzing data is the first step to producing a fatigue curve. In this video, we take field data from an engine run-up and review it in the VibrationVIEW software. The recorded waveform is opened and played back to analyze the waveform and spectrum.

Video 2 of 3

GM Case Study - FDS - Part 2 thumbnail

GM Case Study - FDS - Part 2

In this video, we transform the recorded data into a random power spectral density curve and compare the “average” method to our new Fatigue Damage Spectrum method. We also measure kurtosis for consideration in the FDS transformation.

Video 3 of 3

GM Case Study - FDS - Part 3 thumbnail

GM Case Study - FDS - Part 3

We use FDS to address the age-old question of “is random or sine testing more severe?” This question was addressed several years ago in one of our technical articles where a user asked, “given both a sine test and a random test, how can I determine which is the more severe test?”

Comparison of Ford Mustang Data

Ford turned to Vibration Research when it experienced a part failure in its testing lab and needed to confidently ensure the same wouldn’t happen in the field.

Mustang Comparison Project Description
Red Mustang Damage Calculation
Green Mustang Damage Calculation
Export Damage Data to Excel
Graph Excel Data

Ford Motor Case Study General Motors Case Study

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